1. Field of the Invention
The present invention relates to a vibration generator for use in a portable terminal or the like. More specifically, the present invention pertains to a vibration generator in which a vibrating body reciprocatingly vibrated by magnetic fields is supported by a leaf spring.
2. Description of the Related Art
A portable terminal such as a cellular phone or the like includes a vibration generator capable of notifying a user of arrival of an incoming call. Different types of vibration generators have heretofore been developed. For example, there is known a vibration generator in which an eccentric weight is attached to a rotating shaft. The vibration generator of this type generates vibrations by rotating the eccentric weight with a motor. In the vibration generator of this type, it is however difficult to reduce the thickness thereof. Moreover, the vibration generator of this type suffers from problems in that the vibration generator is low in durability and tends to generate noises during a long-time use.
As a solution to these problems, there is available a vibration generator that reciprocatingly vibrates a vibrating body using the magnetic fields formed by a coil and a magnet.
Japanese Patent Application Publication No. 2002-200460 discloses a technology on a vibration actuator. The vibration actuator includes a fixing portion. The vibration actuator includes a plurality of magnets and a vibrating body having a yoke for closing the magnetic fluxes generated by the magnets. The vibration actuator further includes a plurality of elastic members for movably holding the vibrating body in the fixing portion. The vibration actuator further includes a coil interlinking with the magnetic fluxes generated by the magnets. If an electric current flows through the coil, the coil generates a thrust force between the fixing portion and the vibrating body so that the vibrating body can vibrate in a specified vibration direction.
In the technology disclosed in Japanese Patent Application Publication No. 2002-200460, the vibrating body is held by the elastic member arranged at the opposite sides of the vibrating body in the vibration direction of the vibrating body. The elastic member is formed by joining one longitudinal ends of two band-like leaf springs and bending the leaf springs from the joint portion at an acute angle. Alternatively, the elastic member may be formed by bending the longitudinal intermediate portion of a single band-like leaf spring at an acute angle. In other words, the elastic member includes two component parts formed into a plurality of layers in the vibration direction of a vibrating unit. The vibrating unit is held by the elastic member at the outer sides of the vibration direction.
PCT Patent Application Publication No. 2010/026883 discloses a technology on a linear motor and a cellular phone employing the linear motor. The linear motor includes a spiral coil and a vibrating body arranged in an opposing relationship with the spiral coil. The spiral coil includes a first portion extending in a direction orthogonal to the moving direction of the vibrating body and a second portion extending parallel to the moving direction of the vibrating body. The magnitude of the magnetic fluxes formed by the first portion is larger than the magnitude of the magnetic fluxes formed by the second portion.
In the technology disclosed in PCT Patent Application Publication No. 2010/026883, the vibrating body is held by leaf springs bent at an acute angle and arranged at the opposite sides of the vibrating body in the vibration direction of the vibrating body. In this technology, the elastic member includes two component parts formed into a plurality of layers in the vibration direction of a vibrating body. The vibrating body is held by the elastic member at the outer sides of the vibration direction.
U.S. Patent Application Publication Nos. 2010/0213773 and 2011/0089772 discloses a technology on a linear vibrator. The linear vibrator includes a housing, a vibrating body supported by an elastic member, and a coil arranged within the housing.
The elastic member disclosed in U.S. Patent Application Publication No. 2010/0213773 includes an attachment portion attached to a circumferential wall surface and an arm portion provided with a holding portion. The attachment portion and the arm portion are arranged parallel to each other and are connected to each other by a U-like connecting portion. In the elastic member disclosed in U.S. Patent Application Publication No. 2011/0089772, a holding portion is detachably attached to an arm portion. In the technology disclosed in U.S. Patent Application Publication Nos. 2010/0213773 and 2011/0089772, the vibrating body is supported by an elastic member having a complex shape at the outer sides of the vibration direction.
In the technologies disclosed in Japanese Patent Application Publication No. 2002-200460, PCT Patent Application Publication No. 2010/026883, U.S. Patent Application Publication No. 2010/0213773 and U.S. Patent Application Publication No. 2011/0089772, however, the ratio of the dimension of the elastic member of the leaf spring or the like to the gap between the circumferential wall surfaces supporting the elastic member in the vibration direction of the vibrating body becomes relatively large. For that reason, the dimension of the vibrating body in the vibration direction is limited by the dimension of the elastic member. This reduces the degree of freedom in designing the vibrating body. If the degree of freedom in designing the vibrating body is reduced, it becomes difficult to generate vibrations as desired, depending on the kinds of portable terminals employing the vibration generator.